1. Field of the Invention
This invention relates to ink jet type printers, and particularly to an ink jet type recording unit with an ink jet head (hereinafter referred to merely as "a head", when applicable) and the structure of a carriage supporting the ink jet type recording unit, and more particularly to an ink jet type recording unit which has an ink jet type recording head and an ink cartridge as one unit and can be mounted on or demounted from the carriage when required, and to the connection of the ink jet type recording unit with the carriage.
2. Related Art
In general, an ink jet printer comprises: a carriage which is reciprocated while being guided by a guide shaft laid across the direction of conveyance of a printing sheet; and an ink jet head which is mounted on the carriage to jet ink onto the printing sheet.
Some of the conventional ink jet printers are designed so that the ink jet head and the ink cartridge are provided as one unit, which is detachably mounted on the carriage.
In the conventional ink jet printers thus designed, it is not permitted to connect the unit directly to the carriage by soldering, and therefore wiring must be suitably made to drive the head.
In this connection, Japanese Patent Application (OPI) No. 104643/1991 has disclosed the following printer: As shown in FIG. 28, one end portion 2 of a flexible printed cable (hereinafter referred to as "an FPC", when applicable) is set on a carriage 1, and a unit 3 has a base board 3a which is connected to the end portion 2 of the FPC under pressure. Hence, the unit 3 can be detachably mounted on the carriage 1. The other end portion of the FPC is connected to the control board in the printer body.
In FIG. 28, reference numeral 4 designates a lever which is operated by the operator. The lever 4 is swingably supported by supporting portions 1a and 1a of the carriage 1.
Further in FIG. 28, reference numeral 5 designates a hook member. The hook member 5 includes: a hook 5b which is engageable with an engaging portion 3b of the unit 3; and a base portion 5a which is engaged with a plate cam 4a of the lever 4.
The unit 3 is mounted on the carriage 1 as follows: The hook member 5 is moved in the direction of the arrow X1 by turning the lever 4. Thereafter, the unit 3 is placed on the carriage 1 in such a manner that a protrusion 3c extending from the lower end portion of the unit is abutted against a supporting portion 1c of the carrier, and an engaging portion 3b of the unit is engaged with the hook 5b of the hook member. The unit 3 thus placed is slightly inclined in the direction of the arrow a1. Under this condition, the hook member 5 is moved in the direction of the arrow X2 by turning the lever 4, as a result of which, with the hook 5b firmly engaged with the engaging portion 3b of the unit, the unit 3 is turned in the direction of the arrow a2, so that the base board 3a of the unit is pushed against the end portion 2 of the FPC. Thus, the unit 3 has been fixedly mounted on the carriage 1 as shown in FIG. 28.
In the above-described printer, it is essential to positively connect the base board 3a to the end portion 2 of the FPC. For this purpose, in the printer, a rubber pad 6 is provided behind the end portion 2 of the FPC in such a manner that the rear portion of the pad 6 is supported by a plate 1d formed on the carriage, while the hook member 5 is urged in the direction of the arrow X2 by a spring 8, whereby the base board 3a is pushed against the end portion 2 of the FPC under pressure.
However, the above-described conventional printer suffers from the following problems: In mounting the unit 3 on the carriage; that is, in connecting the end portion 2 of the FPC to the base board 3a, the unit 3 inclined in the direction of the arrow a1 is rotated in the direction of the arrow a2. As the unit 3 is rotated in this way, the base board 3a is gradually pushed against the end portion 2 of the FPC; in other words, the base board 3a and the end portion 2 of the FPC are gradually connected with each other beginning with their lower ends as indicated at b1 (towards their upper ends as indicated at b2).
Hence, the base board 3a and the end portion 2 are liable to be non-uniformly connected to each other. If the connection of the base board 3a to the end portion 2 is not uniform, then the electrical connection of the head and the carriage may be not reliable.
The connection of the base board 3a and the end portion 2 of the FPC may be made uniform by increasing the pressing force of the rubber pad 6 supporting the end portion 2. However, the increasing of the pressing force of the rubber pad 6 is limited, depending on the mechanical strengths of the carriage 1 and other components.
That is, in the above-described printer, it is difficult to uniformly connect the base board 3a and the end portion 2 of the FPC to each other.
The ink jet type printer performs a printing operation while forming dots on a recording medium with ink droplets jetted from its ink jet nozzles. Hence, with the printer, a monochromatic printing operation or a color printing operation can be readily achieved by using printing inks different in color.
In this connection, an ink jet type printer has been put in practical use in which a monochromatic printing recording head and a color printing recording head are mounted on the carriage. The printer of this type is advantageous in that one printer can provide not only monochromatic prints such as text prints but also color prints such as color graphic prints. However, the printer is not suitable for a user who uses it mainly for the monochromatic printing operation. That is, the maintenance of the color printing recording head is rather troublesome to him because he does not so frequently use it.
In order to overcome the above-described difficulty, an ink jet type recording apparatus has been proposed in the art in which an ink cartridge and an ink jet type recording head are provided as one recording unit, and a recording unit suitable for printing given recording data is detachably mounted on the carriage.
The ink jet type recording apparatus thus proposed is advantageous in that a desired printing operation can be achieved by replacing the recording unit with one suitable for the printing operation, and that the recording units which are not in use can be sealingly stored in the casings, so that they are free from maintenance.
However, the ink jet type recording apparatus is still disadvantageous in that, when the ink in the cartridge is used up, it is necessary to replace not only the ink jet type recording head but also the ink cartridge, which results in an increase in printing cost.
In order to overcome the above-described difficulties, an ink jet type recording unit has been proposed in the art in which an ink cartridge accommodating chamber is provided in a frame in which an ink jet type recording head is set, so that the ink cartridge can be readily replaced with another one.
However, the employment of this type of ink jet recording unit gives rise to another problem. That is, when the ink cartridge is replaced with another one, after which the ink jet recording unit is removed from the carriage, air is allowed to enter the recording head during loading or unloading of the ink cartridge. If the recording head including the air is used as it is, then the ink discharging operation becomes unsatisfactory, which makes it impossible to perform or continue the printing operation.